AC/DC power conversion is used in many industrial, commercial, and personal electronic applications. AC/DC conversion involves some inherent inefficiency in terms of power lost between an AC input and a DC output. While some of this inefficiency is inescapable, some inefficiency may also be due to inductance and/or capacitance that reacts against the alternating current, which may be reduced or eliminated with a power factor corrector (PFC). A PFC may be controlled in one of various control modes, such as a Critical Conduction Mode (CrCM) or a Continuous Conduction Mode (CCM), which may be governed by a PFC controller.
CrCM typically provides a lower average output current and may typically be used for low power applications, such as under around 300 watts (W). CrCM provides variable switching frequency and a constant on-time for a gate signal, where the gate signal is switched every time the inductor current of an inductor goes to zero. CrCM thus requires relatively little calculation and is easy to implement. CCM typically provides a higher average output current and is typically used for higher power applications, such as over around 300 watts (W). CCM provides constant switching frequency and variable on-time for the gate signal, where the gate signal switching is based on an average current control method. CCM thus requires more calculation than CrCM.